In case that a conventional CO2 concentration measurement device measures a concentration of CO2 of a sample gas whose CO2 concentration is relatively low such as air or the like, a high accuracy is required. Then there is a case that the measurement accuracy is secured by conducting a drift correction or a zero correction on the CO2 concentration measurement device. This correction is conducted by measuring a zero gas whose concentration of CO2 as being a measuring object or a concentration of other measurement interference component (for example, water in case of measuring the CO2 concentration by the infrared spectroscopy) is substantially zero.
There are two cases; one is to supply the zero gas by the use of a gas cylinder and the other is, as shown in Japanese Unexamined Patent Application Publication No. 2000-180364, to use a zero gas refiner to remove CO2 or other measurement interference component from the air or the sample gas by the use of an adsorbent so as to refine the zero gas whose CO2 concentration is substantially zero.